MRI technology utilizes magnetism and radio frequency for imaging of patients for medical diagnosis and research. Electromagnetic interference (EMI) that is generated in the process of MRI negatively affects other devices in its vicinity such as medical electrical devices, computers, data transfer components, other scanning devices, etc. In addition EMI generated from an external source such as electric lines, television and radio signals, elevators, etc., can impede MRI operation and results.
Facilities providing MRI services build specially designed rooms that allow MRI procedures to be shielded from these interferences, while preventing leakage of the same interferences to the outside.
This shielding may include passive or active components to achieve magnetic and RF shielding. For example, to achieve RF shielding, the walls, floor and ceiling are built from sheets of conductive metal such as copper, aluminum, etc., including a door that maintains a closed circuit with the walls. Magnetic shielding could be provided by constructing a magnetic shield around the RF shield. A passive solution involves using magnetic shielding material, typically metal or metal alloy. These materials would need to be comprised of a very high permeability material such as “mu-metal”. The second option would be an active magnetic cancellation system, that would typically include a magnetometer, controller, amplifier and compensation coils. This solution tends to be costly and requires adjusting and handling.
An MRI scanner utilizes a very strong magnet, thus iron-containing unrestrained objects are drawn, making them airborne, into the magnet's bore. This hazardous phenomenon is known as the projectile, or missile, effect, which can potentially result in serious or fatal injuries to individuals in the scanner room. Numerous severe accidents were recorded at MRI facilities because of pulled iron-containing objects. Keeping the MRD bore open for the passage of medical equipment may leave a space through which projectile objects could enter.
Many patients are in need of medical support or monitoring during MRI. These include neonates, sedated patients, or other medically unstable patients. It is of critical importance to maintain life support and also to monitor conditions of these patients when undergoing MRI. Many of the life support devices, environmental conditions controlling devices and medical monitoring devices utilize electrical circuits that may be interrupted by RF and magnetic fields.
In order to provide a passage for systems such as air conditioning, electrical wiring, communication devices, medical equipment, etc., into EMI shielded rooms, means such as waveguide attenuators and RF filters are used. All fluid and air passing tubes are threaded through a conduit that is configured to attenuate EMI, and all electrical or conductive wiring is connected through an RF filter to avoid coupling of RF to the conductive wire.
There is a long felt need for an apparatus that will provide RF and magnetic shielding, to the MRD and from the MRD. Further there is need for a passage that allows the patient's MRI procedure to take place while allowing passage for medical and life supporting equipment without compromising this shielding. In addition, there is a need for an apparatus that is easy to maneuver and will provide a physically shielded environment for the patient.